What is the enthalpy sign for exothermic reactions?

Exothermic reactions are characterized by the release of heat energy to the surroundings, leading to a decrease in the enthalpy of the system. In thermodynamic terms, the change in enthalpy (ΔH) for an exothermic process is negative. This sign indicates that energy is being produced and released rather than absorbed.

When reactants undergo an exothermic reaction, they usually transform into products that are at a lower energy state than the reactants. As a result, the excess energy is expelled, often in the form of heat. In summary, because exothermic reactions result in a net release of energy, the enthalpy change is expressed as a negative value, reflecting the energy lost to the environment. This is the fundamental reason why the correct answer is that the enthalpy sign for exothermic reactions is negative.